First, wash and dry your lemons. Since you're going to be using the peel exclusively, you want to make sure they don't have any residue on them. Next, peel your lemons (a vegetable peeler works perfectly for this job) - you don't want to get too much of the white pith under the peel, so try to peel as thinly as possible. Put the peels into a large glass container. Add the alcohol, making sure that it completely covers the peels. Let the mixture steep for 10 days, or up to 3 weeks.
Place a colander inside of a large bowl. Pour the alcohol mixture into the colander and drain, using a wooden spoon to press out any excess liquid from the peels. Discard the peels.
In a large saucepan, combine the water and sugar over low heat, stirring occasionally, until the sugar is dissolved and the syrup is clear. Remove from heat and let cool to room temperature, then add the simple syrup to the alcohol mixture and stir to combine.
Place a wire mesh strainer over a large, clean bowl and place a coffee filter inside the mesh strainer. Slowly pour the limoncello through the coffee filter. Once the amount of liquid straining through slows down considerably or stops, replace the coffee filter with a new one and continue until all of the limoncello has been filtered, replacing coffee filters as needed.
Next, filter again and fill the bottles as follows: Place a funnel into the mouth of the bottle you'll use for your finished limoncello. Place a coffee filter inside the funnel, and slowly pour the limoncello through the coffee filter to fill the bottle. Seal the bottle(s) and store in the freezer indefinitely.
Notes
*Note: If you can't obtain grain alcohol where you live, you can substitute 100-proof vodka. Most vodkas are sold in 750mL bottles (versus the 1 liter of grain alcohol called for in the recipe). If this is the size you purchase, adjust the rest of your ingredients as follows: 8 lemons, 4 cups water and 3 cups sugar.Nutritional values are based on one litre